Email updates

Keep up to date with the latest news and content from BMC Microbiology and BioMed Central.

Open Access Highly Accessed Research article

Isolation and genomic characterization of SfI, a serotype-converting bacteriophage of Shigella flexneri

Qiangzheng Sun1, Ruiting Lan2, Yiting Wang1, Jianping Wang1, Yan Wang1, Peijing Li1, Pengcheng Du1 and Jianguo Xu1*

Author affiliations

1 State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, China CDC, P.O. Box 5, Beijing, Changping, China

2 School of Biotechnology and Biomolecular Sciences, University of New South Wales, 2052, Sydney, NSW, Australia

For all author emails, please log on.

Citation and License

BMC Microbiology 2013, 13:39  doi:10.1186/1471-2180-13-39

Published: 17 February 2013

Abstract

Background

All Shigella flexneri serotypes except serotype 6 share a common O-antigen tetrasaccharide backbone and nearly all variations between serotypes are due to glucosyl and/or O-acetyl modifications of the common O unit mediated by glycosyltransferases encoded by serotype-converting bacteriophages. Several S. flexneri serotype-converting phages including SfV, SfX, Sf6 and SfII have been isolated and characterized. However, S. flexneri serotype-converting phage SfI which encodes a type I modification of serotype 1 (1a, 1b, 1c and 1d) had not yet been characterized.

Results

The SfI phage was induced and purified from a S. flexneri serotype 1a clinical strain 019. Electron microscopy showed that the SfI phage has a hexagonal head and a long contractile tail, characteristic of the members of Myoviridae family. SfI can convert serotype Y to serotype 1a and serotype X to serotype 1d, but cannot convert 10 other S. flexneri serotypes (1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, Xv) tested, suggesting that SfI has a narrow host range. Similar to other S. flexneri serotype-converting phages, SfI integrates into the tRNA-thrW gene adjacent to proA of the host chromosome when lysogenized. The complete sequence of the SfI genome was 38,389 bp, encoding 66 open reading frames and two tRNA genes. Phage SfI shares significant homology with S. flexneri phage SfV, Escherichia coli prophage e14 and lambda, and is classified into the lambdoid phage family. SfI was found to use a cos mechanism for DNA packaging similar to that of phage SfV.

Conclusions

SfI contains features of lambdoid phages and is closely related to S. flexneri phage SfV, E. coli prophage e14 and lambda. The characterization of SfI enhances our understanding of serotype conversion of S. flexneri.